An important trend in modern micro-electronics is to reduce the size of an individual node (e.g., a transistor) in a circuit and its required operating voltage so as to increase its operating speed. This trend leads to a smaller node capacitance and therefore a smaller critical charge, which is the minimum electron charge disturbance that will change the logic level of a node.
The reduction of critical charge increases the chance of a circuit (e.g., a DRAM device) experiencing soft errors. A soft error is a wrong signal or datum caused by something other than a defective component in a circuit resulting from mistakes in circuit design or manufacture. One cause of soft error is environmental factors. For example, high-energy neutrons in cosmic rays can induce soft errors via secondary ions (e.g., positively charged alpha particles) produced when the neutrons collide with silicon nuclei.
Therefore, there is a need for semiconductor design and manufacture methodologies that can reduce the soft error rate (SER) of a circuit without adversely affecting its performance.